Levin-Epstein Rebecca, Qiao-Guan George, Juarez Jesus E, Shen Zhouhuizi, Steinberg Michael L, Ruan Dan, Valle Luca, Nickols Nicholas G, Kupelian Patrick A, King Christopher R, Cao Minsong, Kishan Amar U
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, United States.
Case Western Reserve School of Medicine, Cleveland, OH, United States.
Front Oncol. 2020 Apr 16;10:539. doi: 10.3389/fonc.2020.00539. eCollection 2020.
To assess the optimal planning target volume (PTV) margins for stereotactic body radiotherapy (SBRT) of prostate cancer based on inter- and intra-fractional prostate motion determined from daily image guidance. Two hundred and five patients who were enrolled on two prospective studies of SBRT (8 Gy × 5 fractions) for localized prostate cancer treated at a single institution between 2012 and 2017 had complete inter- and intra-fractional shift data available. All patients had scheduled kilovoltage planar imaging during SBRT with rigid registration to intraprostatic fiducials prior to each of four half-arcs delivered per fraction, as well as cone beam CT verification of anatomy prior to each fraction. Inter- and intra- fractional shift data were obtained to estimate the required PTV margins based on the classic van Herk formula. Inter- and intra-fractional motion were compared between patients with and without severe toxicities using the independent two-sample Wilcoxon test. The margins required to account for inter-fractional motion were estimated to be 0.99, 1.52, and 1.45 cm in lateral (LR), longitudinal (SI), and vertical (AP) directions, respectively. The margins required to account for intra-fractional motion were estimated to be 0.19, 0.27, and 0.31 cm in LR, SI and AP directions, respectively. Large intra-fractional shifts were mostly observed in the SI and AP directions, with 2.0 and 5.4% of patients experiencing average intra-fractional motion >3 mm in the SI and AP directions, respectively, compared with none experiencing mean shifts >3 mm in the LR direction. Six patients experienced grade 3 gastrointestinal or genitourinary toxicity. There were no significant differences in mean inter- or intra-fractional motion in any of the cardinal directions compared to patients without severe toxicity (inter-fractional = 0.46-0.99, intra-fractional = 0.10-0.84). The inter- and intra-fractional margins estimated from this study are in line with prior reported values. Intra-fractional prostate motion was generally small with larger margins required for the SI and AP directions, notably just slightly exceeding the commonly used 3 mm posterior PTV margin even with realignment between half-arcs. Development of severe toxicity was not significantly associated with the degree of inter- or intra-fractional motion.
基于每日图像引导确定的分次间和分次内前列腺运动，评估前列腺癌立体定向体部放疗（SBRT）的最佳计划靶区（PTV）边界。2012年至2017年期间，在单一机构接受SBRT（8 Gy×5次分割）治疗局限性前列腺癌的两项前瞻性研究中入组的205例患者，有完整的分次间和分次内移位数据。所有患者在SBRT期间安排了千伏平面成像，在每次分割的四个半弧中的每一个之前与前列腺内基准点进行刚性配准，以及在每次分割之前进行锥形束CT解剖结构验证。获得分次间和分次内移位数据，以根据经典的范·赫克公式估计所需的PTV边界。使用独立的两样本Wilcoxon检验比较有和没有严重毒性的患者之间的分次间和分次内运动。考虑分次间运动所需的边界在横向（LR）、纵向（SI）和垂直（AP）方向上分别估计为0.99、1.52和1.45 cm。考虑分次内运动所需的边界在LR、SI和AP方向上分别估计为0.19、0.27和0.31 cm。大部分较大的分次内移位在SI和AP方向上观察到，分别有2.0%和5.4%的患者在SI和AP方向上经历平均分次内运动>3 mm，而在LR方向上没有患者经历平均移位>3 mm。6例患者出现3级胃肠道或泌尿生殖系统毒性。与没有严重毒性的患者相比，在任何主要方向上的平均分次间或分次内运动均无显著差异（分次间=0.46 - 0.99，分次内=0.10 - 0.84）。本研究估计的分次间和分次内边界与先前报道的值一致。分次内前列腺运动通常较小，SI和AP方向需要更大的边界，即使在半弧之间重新对齐，也仅略超过常用的3 mm后PTV边界。严重毒性的发生与分次间或分次内运动程度无显著关联。
